Pressure monitor and transducer

ABSTRACT

A pressure monitor and transducer, usable as an accelerator for dry pipe sprinkler systems includes a diaphragm separating a closed chamber for another chamber which communicates with the pressure system to be monitored. A controlled leakage valve is mounted centrally in the diaphragm and is linked to a poppet valve which separates the pressurized sprinkler system from the underside or intermediate chamber of a water valve to the system. The force exerted on the diaphragm by fluid pressure in the closed chamber is concentrated in a very small area on the controlled leakage valve to prevent malfunctions caused by dirt and to assure consistent performance.

United States Patent [191 [111 3,785,440 Shea 131111. 115, 11974 PRESSURE MONITOR AND TRANSDUCER Primary ExaminerAllen N. Knowles Inventor: Edward T. Shea, Huntington, NY.

The Reliable Automatic Sprinkler Company, Inc., Mt. Vernon, N.Y.

Filed: May 25, 1972 Appl. No.: 256,923

Assignee:

11.8. C1 169/20, 169/17, 251/612 Int. Cl. A62c 37/02 Field of Search....-. 169/17, 20, 22;

References Cited UNITED STATES PATENTS 6/1932 Benson 169/17 10/1932 Griffith 169/17 6/1971 Juliano 169/17 Assistant Examiner-A. Kashnikow Attorney-Granville M. Brumbaugh et a1.

[57] ABSTRACT A pressure monitor and transducer, usable as an accelerator for dry pipe sprinkler systems includes a diaphragm separating a closed chamber for another chamber which communicates with the pressure system to be monitored. A controlled leakage valve is mounted centrally in the diaphragm and is linked to a poppet valve which separates the pressurized sprinkler system from the underside or intermediate chamber of a water valve to the system. The force exerted on the diaphragm by fluid pressure in the closed chamber is concentrated in a very small area on the controlled leakage valve to prevent malfunctions caused by dirt and to assure consistent performance.

30 Claims, 2 Drawing Figures PATENTEDJAHI W4 3', 785.440

SHEET 2 0F 2 Imuu.

PRESSURE MONITOR AND TRANSDUCER BACKGROUND OF THE INVENTION It is currently standard practice to install overhead sprinkler systems in areas where there is a risk of fire damage. The sprinkler system is intended to quickly extinguish the fire and to prevent its spread and thereby save lives and protect property. As a further inducement for property owners to install these overhead sprinkler systems, the insurance companies will normally give their lowest rates on buildings protected by approved sprinkler systems. v

To provide sprinkler protection for unheated buildingsand facilities, it is necessary to provide a sprinkler system whose pipes are normally filled with air or nitrogen under pressure and empty of water which would freeze in cold weather. When a tire occurs, the fusible element in the sprinkler head nearest the fire melts and opens the sprinkler through which the air in the system escapes, causing the system. air pressure to drop. A

clapper valve at the water inlet to the system is normally held closed by the system air pressure, but when the system air pressure has dropped sufficiently, the clapper valve opens and admitsvwater into the system and through the open sprinkler head to extinguish the fire.

The fundamental deficiency of these dry pipe sprinkler systems is the delay between opening of the first sprinkler head and delivery of water to the fire. This delay is the combined result of the large volume of air in the pipes and the structure of the clapper valve which remains closed until a substantial pressure drop in the system is sensed. In a'system having a large capacity, the rate of flow of escaping air through a single open sprinkler head, although equal to the rate of escape from a small capacity system, causes a percentage decrease in the total mass of air in the systems which is much lower than the same rate of escape would cause in a low capacity system, so the pressure in the system decreases at such a low rate that before the clapper valve functions, the fire may have had a chance to spread over a large area.

To speed the operation of theclapper valve, a device known as an accelerator is installed in the systems. An accelerator is a pressure sensitive transducer that, after sensing a small pressure drop in the sprinkler system air pressure, opens the underside or intermediate chamber of the clapper valve to the systemair pressure to immediately produce the pressure conditions around the clapper valve, namely, a higher pressure behind than in front, that will cause it to open.

In the accelerator, the pressure difference is sensed by a diaphragm separating an upper closed chamber from the system air pressure in a sensed chamber. The upper chamber is brought into pressure equilibrium with the system and then, when the system air pressure drops as occurs when a sprinkler head opens, a different force is established on the diaphragm from the higher pressure in the closed chamber which is used to open a poppet valve which either vents the pressure from the system or directs that pressure to the clapper valve to assist the speedy opening thereof.

To prevent normal pressure drops in the system from causing unwanted flooding of the system, it it necessary to provide a means for controlled pressure leakage from the closed chamber back into the system. This will prevent the accelerator from being actuated by a normally occuring drop in the system pressure, caused for example by normal temperature changes within the building which occur between day and night. It is necessary, however, that means be provided for controlling the rate of leakage from the upper chamber. If the leakage rate is too fast, the accelerator will be insensitive to low rate pressure drops in the system, such as occur when one remote sprinkler head opens in a large capacity system. Conversely, if the leakage rate is too low the system will be too sensitive and will be actuated by normally occuring pressure drops in the system. This will allow the system to flood with water which will freeze in cold weather and render the sprinkler system useless. Therefore, control over the leakage rate from the upper chamber is essential to the operation of a predictable and reliable sprinkler system.

The operating characteristics of accelerators have been made the subject of industry-wide standards which must be met before the insurance companies will approve low rate insurance for a property protected with such systems. For example, the operating characteristics necessary to qualify for Underwriters Laboratory acceptance are as follows:

at a rate of pressure drop'caused by opening a single 56 inch sprinkler head in systems having the capacities listed below, each tested at 25, 35, and 50 PSI, the accelerator must trip within the times listed below and at a drop in the system pressure not to exceed 5 PSI.

System Capacity (gaL) Time to trip (sec.) 300 10 The requirements of an accelerator are thus apparent: it must ignore rates of pressure drop in the system which are caused by normal fluctuations of temperature, but it must quickly respond to the rate of pressure drop in the system which occurs when one sprinkler head opens at the most remote end of the system. In large systems this latter rate of pressure drop can be quite low, so the device must be capable of adjustment to reliably distinguish between the pressure drop caused by normally occuring'temperature changes and a pressure drop caused by the opening of a single sprinkler head. This adjustment may be made by changing the volume of the upper chamber, but is most easily and unexpensively made by adjusting the restricted orifice to control the rate of fluid flow therethrough.

One widely used technique for adjusting the accelerator to make the required pressure discrimination is the use of a needle valve between the upper chamber and the system. The needle valve is generally in the form of a narrow tube communicating between the upper chamber and the system and a tapered pin or needle axially mounted in the tube that can be advanced axially in the tube to adjust the open cross-sectional area in the tube through which air can flow. This restricted orifice provides for equalization of pressure between the upper chamber and the system by permitting a certain rate of leakage from the upper chamber through the restricted orifice, and back to the system, when a normal drop in temperature in the system causes the system pressure to drop below the pressure in the upper chamber. In this way, the rate at which the pressure in the system and the upper chamber is allowed to equalize may be regulated, and the sensitivity, that is, the rate of pressure drop in the system at which the accelerator will function, may be selected. The accelerator will then ignore lower rates of pressure drop and will function only when the selected rate or a faster rate of pressure drop is sensed.

Most presently available accelerators are theoretically capable of distinguishing normal from an abnormal rate of pressure drop, but in practice their sensitivity becomes erratic because of their extreme sensitivity to foreign matter. It is not uncommon for tiny particles of grit to be carried into the accelerator by normal inhaling of the upper chamber and to become lodged in and partially block the restricted orifice. This risk of contamination by foreign matter becomes increasing acute after the device has once operated because it is usually then flooded with water from the system and, despite the filter which is normally present, fine particles of grit invariably are carried into the accelerator along with water from the system. The partial blocking of the restricted orifice of the needle valve by foreign matter, reduces the effective cross-sectional flow area of the orifice and thereby substantially increases the sensitivity of the accelerator, resulting in an increased risk of premature actuation of the accelerator and unwanted flooding of the sprinkler system.

Recognizing the problem, most manufacturers specify in their operating instructions that, after operation, the accelerator is to be carefully disassembled and cleaned; nevertheless, it is rarely possible to clean it completely of all traces of foreign matter and after reassembly, the normal inhaling and exhaling of the upper chamber occasionally carries minute particles of grit into the orifice where they become lodged because of the necessarily very small cross-sectional area of the orifice, and this grit changes the sensitivity of the accelerator.

Thus, the most serious defect in presently available accelerators is their erratic sensitivity. The apparent advantage of precise flow rate control afi'orded by the needle valve is not realized in actual practice because of the substantial changes to that precisely adjusted flow rate caused by grit lodging in the needle valve restricted orifice. Since the preset sensitivity is not constant, the prior art accelerators must be adjusted at a lower sensitivity to provide a safety factor against the possibility of increasing sensitivity caused by foreign matter contamination.

There has, therefore, long existed in the art a serious need for an accelerator that is capable of reliably distinguishing a predetermined rate of pressure drop and whose characteristics are unaffected by intrusion of foreign matter within the mechanism.

SUMMARY OF THE INVENTION Accordingly, this invention provides a pressure monitor and transducer, usable as an accelerator, having a unique means for reliably detecting a predetermined rate of pressure change and whose operating characteristics are unaffected by the intrusion of foreign matter into the internal mechanism.

The pressure monitor and transducer includes a body in which is mounted a centrally apertured diaphragm separating a first chamber from a sensed chamber in communication with a pressure system. The structure defining the aperture in the diaphragm bears against the end ofa rod which links the diaphragm with a signal generating device. When the system and the first chamber are being brought into pressure equilibrium, the

pressure differential acting on the diaphragm will lift the diaphragm slightly off the end of the rod to lessen the resistance to fluid flow through the aperture and allow the first chamber quickly to reach pressure equilibrium with the system. When the first chamber pressure is equal to the system pressure, the diaphragm will return to its normal position with the opening bearing against the top of the rod thereby restricting the rate of fluid leakage through the aperture. When the system pressure changes faster than the predetermined allowable rate, the force exerted by the differential pressure between the two chambers bearing against the diaphragm will be concentrated at the top of the rod thereby brushing or dislodging any foreign matter which may have lodged in the aperture. The force will be transmitted through the rod to the signal generator to generate a signal for any desired purpose, for example, to trigger an actuator of a water valve to flood a sprinkler system with water.

DESCRIPTION OF THE DRAWINGS A more complete understanding of the invention and its many attendant advantages will become more readily apparent as the same becomes better understood by reference to the following description of a preferred embodiment taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional elevation of an accelerator according to this invention; and

FIG. 2 is a partial cross section along a plane perpendicular to lines 22 in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings wherein like characters designate identical or corresponding parts, and more particularly to FIG. 1 thereof, a pressure monitor and transducer according to this invention is shown embodied as an accelerator having a body 10 and a dome 12 attached to the top surface 13 of the body 10 by screws 14 or the like. A threaded bore 15 is formed in the top of the dome 12 to receive a pressure gage (not shown). 1

A recess 16 is formed in the top surface 13 of the body 10 and a step 18 is formed in the walls of recess 16. A floor 20 having a central opening 19 extends across the bottom of the dome l2 and a recess 22 is formed in the underside surface of the floor 20 with a circular step 24 corresponding in size and coaxially aligned with the step 18 in the recess 16.

A centrally apertured movable partition is interposed between the dome 12 and the recess 16. The preferred form of the movable partition is a circular diaphragm 26 of suitable flexible material, such as nylon reinforced Buna N, through which is formed a central aperture 28. The diaphragm 26 is clamped between the top surface 13 of the body 10 and the undersurface 21 of the dome 12. An exteriorly threaded, axially bored, upstanding ferrule 30 having a radial flange at its lower end, extends through the central aperture 28 and through a central aperture in a plate 32 which abuts against the flange on the end of the ferrule 30. A plate 36, identical to the plate 32, has formed centrally therein a central aperture 38 which receives the ferrule 30. An interiorly threaded cup-shaped nut 40 is screwed onto the ferrule 30 down firmly against the plate 36 to firmly clamp the diaphragm 26 between the plate 32 and the plate 36.

A bore 42, flared at its lower end, is formed in the top of the cup-shaped nut 40 coaxially with the bore 34 in the ferrule 30 and the plate 32. The bore 42 is smaller in diameter than a rod 44 which fits loosely within the bore 34 in the ferrule 30 and snuggly within a bore 46 formed in a plastic guide plug 46 held in an axial opening 50 in the floor 511 of the recess 16. The rod 44 bears at its bottom end against a poppet valve 52, which, when opened, establishes communication between an inlet 54 in fluid communication with the sprinkler system and an outlet 56 in fluid communication with the intermediate chamber of a clapper valve of the sprinkler system (not shown).

The inlet 54 in communication with the sprinkler system in turn communicates via a channel (not shown in FIG. I) with a second or sensed chamber 58 which is defined by the recess 16 and the undersurface of the diaphragm 26 and the plate 32. The floor 51 of the recess 16 forms a separator to prevent pressurized fluid from leaking to the outlet 56 and thereby generating a spurious signal to the clapper valve. Likewise, the guide lug 48 and a sealing ring 59 around the rod 44 maintains fluid pressure isolation of the outlet 56 from the sensed chamber 58 while permitting axial translation of I the rod 44 in the guide plug 48.

In operation, when the sprinkler system is being pressurized, the pressure fills the sensed chamber and exerts a force on the undersurface of the plate 32 which displaces the diaphragm 26 upward to lift the nut 40 off the end of the rod 44, as illustrated in FlG. 1, to substantially lessen the resistance to fluid flow into a first or upper chamber 60. The pressurized air passes from the sensed chamber 58, up between the rod 44 and the walls of the'bore 34 and into the first or upper chamber 60 defined by the dome 12. The low resistance to fluid flow into the upper chamber 60 enables the upper chamber to reach pressure equalization with the system very quickly which is a substantial convenience during installation, resetting and testing of the system. When the system has been pressurized and the upper and the sensed chamber pressures are equal, the diaphragm 26 will relax and the flared end of the bore 42 through the top of the nut 40 will rest against the top of the rod 44 to restrict the passage and increase the resistance to fluid flow.

The interface between the top of the rod 44 and the flared end of the bore 42 may be textured so that interstices are provided for the controlled leakage of pressurized air from the upper chamber 60 back into the system via the sensed chamber 58 when the system air pressure drops below that of the upper chamber pressure. The rate of leakage through these interstices is predetermined by the finish to which the interface is ground. For example, the end of the rod 44 and the flared end of the bore 42 may be very smoothly polished to produce a fluid-tight seal therebetween, while a coarse or rough grinding will leave relatively deep furrowsor grooves at the interface for a high rate of air leakage between the end of the rod and the flared end of the bore 42. Any desired intermediate rate may be selected by grinding the material at the interface to an intermediate finish that will produce that rate. To simplify the manufacturing process, the flared end of the bore 42 is preferably ground to a polished finish and only the end of the rod 44 is textured to provide the desired interstices. By this simple technique the sensitivity of the accelerator, i.e., the rate of pressure drop in the system which will trigger the accelerator, may be adjustably predetermined. I

A principle feature of this structure is its innate property of concentrating the force exerted on the diaphragm 26 by the pressure in the top chamber against the top of rod 44. It is thus possible for a very small pressure difference between the top chamber and the sensed chamber 58 to result in a pressure of substantial magnitude at the interface between the top of the rod 44 and the flared end of the bore 42, which assures that the rod will seat properly therein so that the desired restriction of fluid flow will occur. Another extremely advantageous effect of this concentration of pressure at the interface is the dislodging or crushing of any foreign matter such as dirt or grit that may lodge between the end of rod 44 and the flared end of the bore 42 which would otherwise maintain an undesirable separation therebetween and thereby adverslyincrease the crosssectional flow area of the restricted orifice and thus seriously change the operating characteristics of the device. Most foreign matter that lodges in the interface is dislodged by the relative movement between the end of the rod 44 and the flared end of the bore 42 caused by movement of the diaphragm 26 during normal inhaling and exhaling of the top chamber 60 and by the resulting air flow through the restricted orifice. Any foreign matter that is not dislodged in this manner and remains to prevent the end of the rod 44 from properly seating in the flared end of the bore 42 will be crushed by the concentrated force at the head of the rod 44. This ability to crush or dislodge any dirt that may lodge in the opening affords a most advantageous insensitivity to the presence of grit and dirt.

To assist the flared end of orifice 42 in seating firmly and properly on the end of rod 44 whenthe diaphragm 26 relaxes and also to assist in the crushing and dislodging of grit lodged in the interface, an auxiliary spring 62 is provided to apply a downward biasing force against the diaphragm 26; The spring 62 is compressed between the top of the plate 36 and a spring retainer formed of three equally spaced upwardly and inwardly extending fingers 61 at the edges of the opening 19 through the floor 20.

Referring now to FIG. 2 the passage previously referred to by which fluid communication between the sensed chamber and the system is established is by means of a channel 64. Channel 64 communicates, via an orifice 66, with a chamber 68, thence via an opening with the inlet 54.

To prevent water and water-borne foreign matter from being carried into the internal mechanism of the accelerator when the system floods with water, the channel 64 is isolated from the inlet 54 by means of the pressure responsive valve structure72. The valve structure 72 includes a diaphragm 74 extending between the chamber 66 and a reference chamber 76 which communicates with outlet 56. Under normal operating conditions, the pressure in the outlet 56 is lower than the system pressure and the poppet valve is closed to maintain the pressure isolation between the inlet and the outlet. The pressure in the reference chamber 76 is therefore lower than the pressure in the chamber 68 and the diaphragm 74 is held in open position displaced toward chamber 76. When the pressure in chambers 68 and 72 are equalized, which occurs when the poppet valve 52 opens to establish fluid communication between the inlet 54 and the outlet 56,-a biasing spring 80 urges the diaphragm 74 into chamber 68 and presses a sealing plug 78 attached centrally to the diaphragm 74 and axially aligned with the opening 66 into the opening 66 to seal the passage 64. A sintered stainless steel filter 82 is fastened in the opening 70 to exclude all foreign matter which may be carried in through the inlet 54 when the system floods with water.

The accelerator described above exhibits remarkably consistent characteristics even in the presence of contamination by foreign particles which would render all other accelerators inoperative. This repeatability permits the setting of the sensitivity of the accelerator substantially at the optimum sensitivity without the neces sity of a safety factor.

Obviously, numerous modifications, variations and applications of the disclosed pressure monitor and transducer are possible in light of the foregoing description. For example, the end of the rod 44 and the flared end of the bore 42 could be polished to a very fine finish or fitted with other fluid sealing devices to effect a complete seal at that'interface, and fluid passage for reverse leakage maybe provided elsewhere through the diaphragm 26. In addition, the transducer could generate a variety of signals in addition to or in place of the mechanical opening of the valve 52 by making the rod 44 an extension of an electrical or fluidic switch element in a circuit that directly opens the clapper valve or performs some other function. Moreover, the invention is also usable with a vacuum system by connecting the inlet from the system to the upper chamber 60, which would then be the sensed chamber, making the second chamber 58 the reference chamber. The relative volumes of the two chambers would be reversed in this application. Thus, it is expressly to be understood that the invention may be practiced otherwise than as described while still remaining within the scope and spirit of the appended claims.

I claim:

I. A pressure monitor and transducer for monitoring a pressure system and signaling when a pressure change of predetermined rate occurs therein, including means defining a first closed chamber, means defining a second chamber, and means for establishing fluid communication between said second chamber and the pressure system to be monitored, wherein the improvement comprises transducer means for sensing a predetermined rate of pressure change between said two chambers and generating a signal when said change is sensed, including:

a movable partition separating said first chamber from said second chamber;

means in said partition defining an aperture therethrough;

signal generating means for generating a signal upon actuation; and

linking means linking said partition and said signal.

generating means and bearing against said aperture defining means to obtain at the interface therebetween i. restriction of said aperture to limit the leakage rate of fluid therethrough,

ii. concentration at said interface, of force acting on said partition to effect dislodgement of any foreign particles that may be blocking said aperture restriction, and

iii. transmission of said force through said linking means to said signal generating means to actuate said signal generating means when the pressure difference between said first and second chambers exceeds a predetermined value.

2. A pressure monitor and transducer as defined in claim 1, further comprising:

surface texturing means at said interface for predetermining the rate of fluid leakage past said restriction.

3. A pressure monitor and transducer as defined in claim 1, further comprising:

biasing means for biasing said aperture defining means and said linking means into contact with each other. I

4. A pressure monitor and transducer as defined in claim 2, wherein said linking means comprises a rod contacting at one end thereof said signal generating means and at the other end normally engaging said partition aperture defining means and thereby restricting the aperture defined thereby.

5. A pressure monitor and transducer as defined in claim 4, further comprising:

separator means for isolating said second chamber from said signal generating means;

guide means for slidably holding said rod for axial translation in said separator means; and

sealing means for sealing said rod in said guide means against leakage of fluid therebetween.

6. A pressure monitor and transducer as defined in claim 2, wherein said partition aperture defining means comprises:

a centrally apertured plate disposed on each side of said partition;

means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and

means extending axially through said member defining a bore communicating with opposite sides of said partition.

7. A pressure monitor and transducer as defined in claim 1, wherein the resistance to fluid flow through said aperture defining means in one direction is substantially less than the resistance to fluid flow through said aperture defining means in'the other direction.

8. A pressure monitor and transducer as defined in claim 1, wherein said linking means and said aperture defining means are movable with respect to each other in normal operation;

wherein said relative movement of said aperture defining means and said linking means and the normal fluid flow through said aperture is effective to dislodge particles of foreign matter that may have lodged between said linking means and said aperture defining means.

9. An accelerator for sensing a predetermined rate of pressure drop in a dry pipe sprinkler system and for triggering an actuator of a water valve to admit water into the dry pipe sprinkler system, comprising:

a. a body having means therein defining i) an inlet ii) a first chamber, and

iii) a second chamber communicating with said inlet;

b. a movable partition separating said first chamber and said second chamber;

c. means for operatively linking said actuator and said partition;

d. means on said partition defining an aperture there through and normally bearing against said linking means to obtain at the interface therebetween i. restriction of said aperture to limit the leakage rate of fluid from said first chamber past said interface to said second chamber,

ii. concentration, at said interface, of force acting on said partition to effect dislodgement of any I foreign particles that may be blocking said aperture restriction, and

iii. transmission of said force through said linking means to trigger said actuator to open said water valve when the pressure difference between said first and second chambers exceeds a predetermined value.

10. 'An accelerator as defined in claim 9, further comprising surface texturing means of said interface for predetermining the rate of fluid leakage past said restriction.

lll. An accelerator as defined'in claim 9, further comprising biasing means for biasing said aperture defining means and said linking means into contact with each other.

12. An accelerator as defined in claim ll), wherein said linking means comprises a rod bearing at one end thereof against said actuator and at the other end normally engaging said partition aperture defining means and thereby restricting the aperture defined thereby.

13. An accelerator as defined in claim 12, further comprising:

guide means for slidably holding said rod for axial translation in said body, and

sealing means for sealing said rod in said guide means against leakage of fluid therebetween.

14. An accelerator as defined. in claim 12, wherein said partition aperture defining means comprises:

a centrally apertured plate. disposed on each side of said partition;

means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and

means extending axially through said member defining a bore communicating with opposite sides of said partition.

15. An accelerator as defined in claim 9, wherein the resistance to fluid flow through said aperture restriction into said first chamber, when the pressure in said system exceeds the pressure in said first chamber by a given pressure differential, is substantially less than the resistance to fluid flow through said aperture restriction out of said first chamber when the pressure in said first chamber exceeds the pressure in said system by said given pressure differential.

16. An accelerator as defined in claim 9, wherein said linking means and said aperture defining means are movable with respect to each other in normal operation;

wherein said relative movement of said aperture defining means and said linking means and the normal inhaling of fluid through said aperture into said first chamber is effective to dislodge particles of foreign matter that may have lodged between said linking means and said aperture defining means.

17. An accelerator, comprising:

a. a body having means therein defining i. an inlet ii. an outlet iii. a first chamber, and

iv. a second chamber communicating with said inlet;

b. a poppet valve separating said inlet and said outlet;

c. a movable partition separating said first chamber and said second chamber;

d. means operatively inking said poppet valve and said partition for transmitting a force from said partition to said poppet valve;

e. means on said partition defining an aperture therethrough and normally bearing against said linking means to obtain at the interface therebetween i. restriction of said aperture to limit the leakage rate of fluid from said first chamber past said interface to said second chamber,

ii. concentration at said interface, of 'force acting on said partition to effect dislodgement of any foreign particles that may be blocking said aperture restriction, and

iii. transmission of said force through said linking means to said poppet valve to open said poppet valve and establish fluid communication between said inlet and said outlet, when the pressure difference between said first and second chambers exceeds a predetermined value.

13. An accelerator as defined in claim 17, wherein the rate of fluid leakage past saidrestriction is predetermined by texturing the material at said interface.

19. An accelerator as defined in claim 18, wherein the rate of fluid leakage past said restriction is predetermined by texturing the material of said linking means at said interface.

20. An accelerator as defined in claim 18, wherein said linking means comprises a rod contacting at one end thereof said poppet valve and at the other end normally engaging said partition aperture defining means and thereby restricting the aperture defined thereby.

21. An accelerator as defined in claim 20, further comprising:

guide means for slidably holding said rod for axial translation in said body, and

sealing means for sealing said rod in said guide means against leakage of fluid therebetween.

22. An accelerator as defined in claim 18, wherein said partition aperture defining means comprises:

a centrally apertured plate disposed on each side of said partition;

means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and

means extending axially through said member defining a bore communicating with opposite sides of said partition.

23. An accelerator as defined in claim 17, wherein the resistance to fluid flow through said aperture restriction into said first chamber, when the pressure in said system exceeds the pressure in said first chamber by a given pressure differential, is substantially less than the resistance to fluid flow through said aperture restriction out of said first chamber when the pressure in said first chamber exceeds the pressure in said system by said given pressure differential.

24. An accelerator as defined in claim 17, wherein said linking means and said aperture defining means are movable with respect to each other in normal operation;

wherein said relative movement of said aperture defining means and said linking means and the normal inhaling of fluid through said aperture into said first chamber is effective to dislodge particles of foreign matter that may have lodged between said linking means and said aperture defining means. 25. An accelerator as defined in claim 17, further comprising pressure responsive means interposed between said inlet and said second chamber for sealing said second chamber from said inlet when said poppet valve opens.

26. An accelerator for sensing a predetermined rate of pressure drop in a dry pipe sprinkler system and for triggering an actuator of a water valve to admit water into the dry pipe sprinkler system, comprising:

a. a body having means therein defining i. an inlet ii. a first chamber, and

iii. a second chamber communicating with said inlet; b. a movable partition separating said first chamber and said second chamber; 0. means for operatively linking said actuator and said partition; d. means on said partition defining an aperture therethrough and normally bearing against said linking means to obtain at the interface therebetween i. control of the fluid flow from said first chamber to said second chamber when the pressure in said first chamber exceeds or is within a predetermined value of the pressure in said second chamber,

ii. free passage for fluid flow from said second chamber to said first chamber when the pressure in said second chamber exceeds the pressure in said first chamber by said predetermined value,

iii. concentration at said interface of force exerted on said partition by the differential pressure between said first and second chambers; and

iv. transmission of said force through said linking means to trigger said actuator to open said water valve when the pressure difference between said first and second chambers exceeds a predetermined value.

27. An accelerator as defined in claim 26, further comprising biasing means for biasing said aperture defining means and said linking means into contact with each other.

28. An accelerator as defined in claim 26, wherein said linking means comprises a rod hearing at one end thereof against said actuator and at the other end normally engaging said partition aperture defining means and thereby controllingfluid flow therethrough.

29. An accelerator as defined in claim 28, further comprising:

guide means for slidably holding said rod for axial translation in said body, and

sealing means for sealing said rod in said guide means against leakage of fluid therebetween.

30. An accelerator as defined in claim 28, wherein said partition aperture defining means comprises:

a centrally apertured plate disposed on each side of said partition;

means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and

means extending axially through said member defining a bore communicating with opposite sides of 

1. A pressure monitor and transducer for monitoring a pressure system and signaling when a pressure change of predetermined rate occurs therein, including means defining a first closed chamber, means definIng a second chamber, and means for establishing fluid communication between said second chamber and the pressure system to be monitored, wherein the improvement comprises transducer means for sensing a predetermined rate of pressure change between said two chambers and generating a signal when said change is sensed, including: a movable partition separating said first chamber from said second chamber; means in said partition defining an aperture therethrough; signal generating means for generating a signal upon actuation; and linking means linking said partition and said signal generating means and bearing against said aperture defining means to obtain at the interface therebetween i. restriction of said aperture to limit the leakage rate of fluid therethrough, ii. concentration at said interface, of force acting on said partition to effect dislodgement of any foreign particles that may be blocking said aperture restriction, and iii. transmission of said force through said linking means to said signal generating means to actuate said signal generating means when the pressure difference between said first and second chambers exceeds a predetermined value.
 2. A pressure monitor and transducer as defined in claim 1, further comprising: surface texturing means at said interface for predetermining the rate of fluid leakage past said restriction.
 3. A pressure monitor and transducer as defined in claim 1, further comprising: biasing means for biasing said aperture defining means and said linking means into contact with each other.
 4. A pressure monitor and transducer as defined in claim 2, wherein said linking means comprises a rod contacting at one end thereof said signal generating means and at the other end normally engaging said partition aperture defining means and thereby restricting the aperture defined thereby.
 5. A pressure monitor and transducer as defined in claim 4, further comprising: separator means for isolating said second chamber from said signal generating means; guide means for slidably holding said rod for axial translation in said separator means; and sealing means for sealing said rod in said guide means against leakage of fluid therebetween.
 6. A pressure monitor and transducer as defined in claim 2, wherein said partition aperture defining means comprises: a centrally apertured plate disposed on each side of said partition; means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and means extending axially through said member defining a bore communicating with opposite sides of said partition.
 7. A pressure monitor and transducer as defined in claim 1, wherein the resistance to fluid flow through said aperture defining means in one direction is substantially less than the resistance to fluid flow through said aperture defining means in the other direction.
 8. A pressure monitor and transducer as defined in claim 1, wherein said linking means and said aperture defining means are movable with respect to each other in normal operation; wherein said relative movement of said aperture defining means and said linking means and the normal fluid flow through said aperture is effective to dislodge particles of foreign matter that may have lodged between said linking means and said aperture defining means.
 9. An accelerator for sensing a predetermined rate of pressure drop in a dry pipe sprinkler system and for triggering an actuator of a water valve to admit water into the dry pipe sprinkler system, comprising: a. a body having means therein defining i) an inlet ii) a first chamber, and iii) a second chamber communicating with said inlet; b. a movable partition separating said first chamber and said second chamber; c. means for operatively linking said actuator and said partition; d. means on said partition defining an aperture therethrough and noRmally bearing against said linking means to obtain at the interface therebetween i. restriction of said aperture to limit the leakage rate of fluid from said first chamber past said interface to said second chamber, ii. concentration, at said interface, of force acting on said partition to effect dislodgement of any foreign particles that may be blocking said aperture restriction, and iii. transmission of said force through said linking means to trigger said actuator to open said water valve when the pressure difference between said first and second chambers exceeds a predetermined value.
 10. An accelerator as defined in claim 9, further comprising surface texturing means of said interface for predetermining the rate of fluid leakage past said restriction.
 11. An accelerator as defined in claim 9, further comprising biasing means for biasing said aperture defining means and said linking means into contact with each other.
 12. An accelerator as defined in claim 10, wherein said linking means comprises a rod bearing at one end thereof against said actuator and at the other end normally engaging said partition aperture defining means and thereby restricting the aperture defined thereby.
 13. An accelerator as defined in claim 12, further comprising: guide means for slidably holding said rod for axial translation in said body, and sealing means for sealing said rod in said guide means against leakage of fluid therebetween.
 14. An accelerator as defined in claim 12, wherein said partition aperture defining means comprises: a centrally apertured plate disposed on each side of said partition; means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and means extending axially through said member defining a bore communicating with opposite sides of said partition.
 15. An accelerator as defined in claim 9, wherein the resistance to fluid flow through said aperture restriction into said first chamber, when the pressure in said system exceeds the pressure in said first chamber by a given pressure differential, is substantially less than the resistance to fluid flow through said aperture restriction out of said first chamber when the pressure in said first chamber exceeds the pressure in said system by said given pressure differential.
 16. An accelerator as defined in claim 9, wherein said linking means and said aperture defining means are movable with respect to each other in normal operation; wherein said relative movement of said aperture defining means and said linking means and the normal inhaling of fluid through said aperture into said first chamber is effective to dislodge particles of foreign matter that may have lodged between said linking means and said aperture defining means.
 17. An accelerator, comprising: a. a body having means therein defining i. an inlet ii. an outlet iii. a first chamber, and iv. a second chamber communicating with said inlet; b. a poppet valve separating said inlet and said outlet; c. a movable partition separating said first chamber and said second chamber; d. means operatively linking said poppet valve and said partition for transmitting a force from said partition to said poppet valve; e. means on said partition defining an aperture therethrough and normally bearing against said linking means to obtain at the interface therebetween i. restriction of said aperture to limit the leakage rate of fluid from said first chamber past said interface to said second chamber, ii. concentration at said interface, of force acting on said partition to effect dislodgement of any foreign particles that may be blocking said aperture restriction, and iii. transmission of said force through said linking means to said poppet valve to open said poppet valve and establish fluid communication between said inlet and said outlet, when the pressure difference between Said first and second chambers exceeds a predetermined value.
 18. An accelerator as defined in claim 17, wherein the rate of fluid leakage past said restriction is predetermined by texturing the material at said interface.
 19. An accelerator as defined in claim 18, wherein the rate of fluid leakage past said restriction is predetermined by texturing the material of said linking means at said interface.
 20. An accelerator as defined in claim 18, wherein said linking means comprises a rod contacting at one end thereof said poppet valve and at the other end normally engaging said partition aperture defining means and thereby restricting the aperture defined thereby.
 21. An accelerator as defined in claim 20, further comprising: guide means for slidably holding said rod for axial translation in said body, and sealing means for sealing said rod in said guide means against leakage of fluid therebetween.
 22. An accelerator as defined in claim 18, wherein said partition aperture defining means comprises: a centrally apertured plate disposed on each side of said partition; means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and means extending axially through said member defining a bore communicating with opposite sides of said partition.
 23. An accelerator as defined in claim 17, wherein the resistance to fluid flow through said aperture restriction into said first chamber, when the pressure in said system exceeds the pressure in said first chamber by a given pressure differential, is substantially less than the resistance to fluid flow through said aperture restriction out of said first chamber when the pressure in said first chamber exceeds the pressure in said system by said given pressure differential.
 24. An accelerator as defined in claim 17, wherein said linking means and said aperture defining means are movable with respect to each other in normal operation; wherein said relative movement of said aperture defining means and said linking means and the normal inhaling of fluid through said aperture into said first chamber is effective to dislodge particles of foreign matter that may have lodged between said linking means and said aperture defining means.
 25. An accelerator as defined in claim 17, further comprising pressure responsive means interposed between said inlet and said second chamber for sealing said second chamber from said inlet when said poppet valve opens.
 26. An accelerator for sensing a predetermined rate of pressure drop in a dry pipe sprinkler system and for triggering an actuator of a water valve to admit water into the dry pipe sprinkler system, comprising: a. a body having means therein defining i. an inlet ii. a first chamber, and iii. a second chamber communicating with said inlet; b. a movable partition separating said first chamber and said second chamber; c. means for operatively linking said actuator and said partition; d. means on said partition defining an aperture therethrough and normally bearing against said linking means to obtain at the interface therebetween i. control of the fluid flow from said first chamber to said second chamber when the pressure in said first chamber exceeds or is within a predetermined value of the pressure in said second chamber, ii. free passage for fluid flow from said second chamber to said first chamber when the pressure in said second chamber exceeds the pressure in said first chamber by said predetermined value, iii. concentration at said interface of force exerted on said partition by the differential pressure between said first and second chambers; and iv. transmission of said force through said linking means to trigger said actuator to open said water valve when the pressure difference between said first and second chambers exceeds a predetermined value.
 27. An accelerator as defined in claim 26, further Comprising biasing means for biasing said aperture defining means and said linking means into contact with each other.
 28. An accelerator as defined in claim 26, wherein said linking means comprises a rod bearing at one end thereof against said actuator and at the other end normally engaging said partition aperture defining means and thereby controlling fluid flow therethrough.
 29. An accelerator as defined in claim 28, further comprising: guide means for slidably holding said rod for axial translation in said body, and sealing means for sealing said rod in said guide means against leakage of fluid therebetween.
 30. An accelerator as defined in claim 28, wherein said partition aperture defining means comprises: a centrally apertured plate disposed on each side of said partition; means for clamping said partition firmly between said plates, including a securing member extending through said apertures in said plates; and means extending axially through said member defining a bore communicating with opposite sides of said partition. 